The present invention relates to an optical probe for observing and measuring optical characteristics of a sample in a minute region by using near-field light, and particularly to an optical waveguide probe made of an optical waveguide and a manufacturing method of the same.
At present, in a scanning near-field optical microscope (hereinafter abbreviated as SNOM), a probe having a sharpened tip and formed of an optical medium is made to approach a measured sample within a wavelength of light, so that the optical characteristic or shape of the sample is measured. As one of this type of devices, a device is proposed in which a tip of an optical fiber probe held vertically with respect to a sample is vibrated horizontally with respect to the surface of the sample, a change of vibration amplitude generated by shear force between the surface of the sample and the tip of the probe is detected through a change of shadow of laser light irradiated to the tip of the probe, and the sample is moved by a fine moving mechanism to make the amplitude constant, so that an interval between the tip of the probe and the surface of the sample is kept constant, whereby a surface shape is detected from the intensity of a signal inputted to the fine moving mechanism, and the measurement of optical transparency of the sample is carried out.
Besides, a scanning near-field atomic force microscope is proposed in which an optical fiber probe formed like a hook is used as a cantilever of the atomic force microscope (hereinafter abbreviated as AFM), and at the same time as an AFM operation, laser light is irradiated to a sample from a tip of the optical fiber probe, so that a surface shape is detected and optical characteristics of the sample are measured (Japanese Patent Unexamined Publication No. Hei. 7-174542). In this optical fiber probe, an optical fiber is used as an optical medium, and the periphery of the optical fiber is covered with a metallic film coating. A probe portion is sharpened, and an aperture is provided at the tip of the probe portion.
Besides, an optical waveguide probe is also known in which an optical waveguide is made of a laminate of a core and a cladding to be constructed like a cantilever, a sharpened probe portion is formed at one end, a support portion for fixing the optical waveguide is formed at the other end, and the optical waveguide at the side of the probe portion has a curved structure.
However, the optical fiber probe used in the SNOM is manufactured by using an optical fiber as a material through many handwork steps, so that there are problems that mass productivity is low, and a shape, such as a tip diameter or a tip angle of a probe portion, or a diameter of an aperture, is irregular. Besides, in order to perform probe scanning at high speed without damage, it is necessary that the resonance frequency of the probe is made high, and the spring constant is made small. However, since the optical fiber is used as the optical medium, there is a problem that it is difficult to miniaturize the probe and to provide the high resonance frequency and the low spring constant.
Further, there is a problem that in the probe in which the optical fiber or optical waveguide is curved, the loss of propagated light occurs at the curved portion, and the propagated light can not be efficiently propagated.
The present invention has been made in view of the above, and it is an object of the invention to provide an optical waveguide probe which is excellent in mass productivity, uniformity, and high speed scanning property, and can efficiently propagate a propagated light, and is to provide a manufacturing method for fabricating the optical waveguide probe.
In order to achieve the above object, an optical waveguide probe of the present invention comprises a cantilever-like optical waveguide, a probe provided at a tip of the optical waveguide and sharpened in a substantially vertical direction with respect to the optical waveguide, a minute aperture provided at a tip of the probe portion, and a bent portion where a vicinity of the tip of the optical waveguide is bent toward a side of the probe, and is characterized in that the bent portion has a deflecting function for deflecting a propagated light in the optical waveguide.
Besides, a deflection angle of the propagated light at the bent portion is 90 degrees or less.
Besides, the bent portion deflects the propagated light by a single surface.
Besides, the single surface is a surface orthogonal to an optical axis plane including an optical axis from the optical waveguide to the minute aperture.
Besides, the single surface is a surface which is not orthogonal to the optical axis plane.
Besides, an angle of the single surface with respect to a plane orthogonal to the optical axis plane and including an optical axis of the waveguide is 45 degrees or less.
The bent portion is bent at a plurality of surfaces substantially symmetrical with respect to an optical axis plane including an optical axis from the optical waveguide to the minute aperture.
Besides, the plurality of surfaces is a plurality of flat surfaces.
Besides, the plurality of flat surfaces is respectively not vertical to the optical axis plane.
Besides, the bent portion includes a reflecting film.
Besides, a guide for positioning an optical element is provided at a support portion of the optical waveguide.
Besides, the guide is a V groove.
According to the above optical waveguide probe, since the propagated light can be efficiently deflected at the bent portion, the efficiency of outgoing light from the minute aperture, or the efficiency of the detection of light at the minute aperture can be improved. Further, since the propagated light having been propagated through the optical waveguide can be condensed to the minute aperture, or to the contrary, since the light from the minute aperture can be collimated, the efficiency can be improved.
In order to achieve the above object, a manufacturing method of an optical waveguide probe according to the present invention comprises a substrate formation step of forming a substrate on which an optical waveguide is deposited, a deposition step of depositing the optical waveguide on the substrate, and a separation step of separating a part of the optical waveguide from the substrate, and is characterized in that in the substrate formation step, the bent-shaped substrate for bending the part of the optical waveguide is formed.
Besides, the substrate formation step is a step of forming the substrate including a lower surface parallel to an optical axis of the optical waveguide, and a plurality of surfaces which are not vertical to the lower surface and are substantially symmetrical with respect to a plane including the optical axis and a normal of the lower surface.
Besides, the substrate formation step is a step of forming the substrate by using an anisotropic etching.
Besides, a manufacturing method of an optical waveguide probe used for a scanning near-field optical microscope uses two substrates bonded to each other through a material having different etching characteristics and is characterized by comprising a step of forming a step portion for bending a part of an optical waveguide on one of the substrates, and a step of forming a guide for an optical element on the other substrates.
Besides, the substrate is a single crystal silicon substrate.
Besides, in the substrates, two single crystal silicon substrates having identical plane orientations are bonded to each other.
Besides, in the substrates, two single crystal silicon substrates having different plane orientations are bonded to each other.
Besides, in the substrates, the substrates are bonded so that an optical axis direction of the waveguide of the substrate forming a mold is coincident with an optical axis direction of the guide of the substrate forming the guide.
Besides, a core of the optical waveguide and a pattern for defining the guide for the optical element are simultaneously formed.
According to the above manufacturing method of the optical waveguide probe, the probe can be fabricated by laminating the optical waveguide on the substrate which becomes the mold, so that the mass productivity, shape reproducibility, and uniformity are improved. Besides, since a small optical waveguide probe can be fabricated, the optical waveguide probe having a low spring constant and a high resonance frequency can be fabricated. Thus, it becomes possible to make high speed scanning without damaging the probe. Besides, it becomes possible to form a bent portion which can efficiently propagate a propagated light.